[GOLF BALL HAVING A POLYURETHANE COVER(Corporate Docket Number PU2156 )]

ABSTRACT

A golf ball having a thermosetting polyurethane cover composed of a blend of polyurethane prepolymers is disclosed herein. The blend may be a dual blend with a TDI-based polyurethane prepolymer blended with a second diisocyanate polyurethane prepolymer, typically a PPDI-based polyurethane prepolymer. The blend may also be a tri-blend with a TDI-based polyurethane prepolymer blended with two other diisocyanate polyurethane prepolymers, typically two different PPDI-based polyurethane prepolymers. The golf ball has a durability of at least 3.5 on a shear test rating of the cover.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation application of co-pending U.S.patent application Ser. No. 10/063,801 filed on May 14, 2002, which is acontinuation application of co-pending U.S. patent application Ser. No.09/710,732, now U.S. Pat. No. 6,435,987, which is a divisionalapplication of U.S. patent application Ser. No. 09/361,912, filed onJul. 27, 1999, now U.S. Pat. No. 6,190,268.

FEDERAL RESEARCH STATEMENT

[0002] [Not Applicable]

BACKGROUND OF INVENTION

[0003] 1. Field of the Invention

[0004] The present invention relates to a cover for a golf ball. Morespecifically, the present invention relates to a golf ball cover layercomposed of a polyurethane formed from a blend of diisocyanateprepolymers.

[0005] 2. Description of the Related Art

[0006] Conventionally golf balls are made by molding a cover around acore. The core may be wound or solid. A wound core typically compriseselastic thread wound about a solid or liquid center. Unlike wound cores,solid cores do not include a wound elastic thread layer. Solid corestypically may comprise a single solid piece center or a solid centercovered by one or more mantle or boundary layers of material.

[0007] The cover may be injection molded, compression molded, or castover the core. Injection molding typically requires a mold having atleast one pair of mold cavities, e.g., a first mold cavity and a secondmold cavity, which mate to form a spherical recess. In addition, a moldmay include more than one mold cavity pair.

[0008] In one exemplary injection molding process each mold cavity mayalso include retractable positioning pins to hold the core in thespherical center of the mold cavity pair. Once the core is positioned inthe first mold cavity, the respective second mold cavity is mated to thefirst to close the mold. A cover material is then injected into theclosed mold. The positioning pins are retracted while the cover materialis flowable to allow the material to fill in any holes caused by thepins. When the material is at least partially cured, the covered core isremoved from the mold.

[0009] As with injection molding, compression molds typically includemultiple pairs of mold cavities, each pair comprising first and secondmold cavities that mate to form a spherical recess. In one exemplarycompression molding process, a cover material is pre-formed intohalf-shells, which are placed into a respective pair of compression moldcavities. The core is placed between the cover material half-shells andthe mold is closed. The core and cover combination is then exposed toheat and pressure, which cause the cover half-shells to combine and forma full cover.

[0010] As with the above-referenced processes, a casting process alsoutilizes pairs of mold cavities. In a casting process, a cover materialis introduced into a first mold cavity of each pair. Then, a core isheld in position (e.g. by an overhanging vacuum or suction apparatus) tocontact the cover material in what will be the spherical center of themold cavity pair. Once the cover material is at least partially cured(e.g., a point where the core will not substantially move), the core isreleased, the cover material is introduced into a second mold cavity ofeach pair, and the mold is closed. The closed mold is then subjected toheat and pressure to cure the cover material thereby forming a cover onthe core. With injection molding, compression molding, and casting, themolding cavities typically include a negative dimple pattern to impart adimple pattern on the cover during the molding process.

[0011] Materials previously used as golf ball covers include balata(natural or synthetic), gutta-percha, ionomeric resins (e.g., DuPont'sSURLYNÂ®), and polyurethanes. Balata is the benchmark cover materialwith respect to sound (i.e. the sound made when the ball is hit by agolf club) and feel (i.e. the sensation imparted to the golfer whenhitting the ball). Natural balata is derived from the Bully Gum tree,while synthetic balata is derived from a petroleum compound. Balata isexpensive compared to other cover materials, and golf balls covered withbalata tend to have poor durability (i.e. poor cut and shearresistance). Gutta percha is derived from the Malaysian sapodilla tree.A golf ball covered with gutta percha is considered to have a harshsound and feel as compared to balata covered golf balls.

[0012] Ionomeric resins, as compared to balata, are typically lessexpensive and tend to have good durability. However, golf balls havingionomeric resin covers typically have inferior sound and feel,especially as compared to balata covers.

[0013] A golf ball with a polyurethane cover generally has greaterdurability than a golf ball with a balata cover. The polyurethanecovered golf ball generally has a better sound and feel than a golf ballwith an ionomeric resin cover. Polyurethanes may be thermoset orthermoplastic. Polyurethanes are formed by reacting a prepolymer with apolyfunctional curing agent, such as a polyamine or a polyol. Thepolyurethane prepolymer is the reaction product of, for example, adiisocyanate and a polyol such as a polyether or a polyester. Severalpatents describe the use of polyurethanes in golf balls. However, golfballs with polyurethane covers usually do not have the distance of othergolf balls such as those with covers composed of SURLYNÂ®materials.

[0014] Gallagher, U.S. Pat. No. 3,034,791 discloses a polyurethane golfball cover prepared from the reaction product of poly (tetramethyleneether) glycol and toluene-2,4-diisocyanates (TDI), either pure TDI or anisomeric mixture.

[0015] Isaac, U.S. Pat. No. 3,989,568 (the '568 patent) discloses apolyurethane golf ball cover prepared from prepolymers and curing agentsthat have different rates of reaction so a partial cure can be made. The'568 patent explains that the minimum number of reactants is three.Specifically, in '568 patent, two or more polyurethane prepolymers arereacted with at least one curing agent, or at least one polyurethaneprepolymer is reacted with two or more curing agents as long as thecuring agents have different rates of reaction. The examples in the '568patent only disclose golf balls having covers that are about 0.025inches thick.

[0016] Dusbiber, U.S. Pat. No. 4,123,061 (the '061 patent)discloses apolyurethane golf ball cover prepared from the reaction product of apolyether, a diisocyanate and a curing agent. The '061 patent disclosesthat the polyether may be polyalkylene ether glycol orpolytetramethylene ether glycol. The '061 patent also discloses that thediisocyanate may be TDI, 4,4″-diphenylmethane diisocyanate (MDI), and3,3″-dimethyl-4,4″-biphenylene diisocyanate (TODI). Additionally, the'061 patent discloses that the curing agent may be either a polyol(either tri- or tetra-functional and not di-functional) such astriisopropanol amine (TIPA) or trimethoylol propane (TMP), or anamine-type having at least two reactive amine groups such as:3,3″dichlorobenzidene; 3,3″dichloro 4,4″diamino diphenyl methane (MOCA);N,N,N″,N″tetrakis (2-hydroxy propyl) ethylene diamine; or Uniroyal″sCuralon L which is an aromatic diamine mixture.

[0017] Hewitt, et al., U.S. Pat. No. 4,248,432 (the '432 patent)discloses a thermoplastic polyesterurethane golf ball cover formed froma reaction product of a polyester glycol (molecular weight of 800-1500)(aliphatic diol and an aliphatic dicarboxylic acid) with apara-phenylene diisocyanate (PPDI) or cyclohexane diisocyanate in thesubstantial absence of curing or crosslinking agents. The '432 patentteaches against the use of chain extenders in making polyurethanes. The'432 patent states, when small amounts of butanediol-1,4 are mixed witha polyester â

the addition results in polyurethanes that do not have the desiredbalance of properties to provide good golf ball covers. Similarly, theuse of curing or crosslinking agents is not desired.

[0018] Holloway, U.S. Pat. No. 4,349,657 (the '657 patent) discloses amethod for preparing polyester urethanes with PPDI by reacting apolyester (e.g. prepared from aliphatic glycols having 2-8 carbonsreacted with aliphatic dicarboxylic acids having 4-10 carbons) with amolar excess of PPDI to obtain an isocyanate-terminated polyesterurethane (in liquid form and stable at reaction temperatures), and thenreacting the polyester urethane with additional polyester. The '657patent claims that the benefit of this new process is the fact that acontinuous commercial process is possible without stability problems.The '657 patent further describes a suitable use for the resultantmaterial to be golf ball covers.

[0019] Wu, U.S. Pat. No. 5,334,673 (the '673 patent) discloses apolyurethane prepolymer cured with a slow-reacting curing agent selectedfrom slow-reacting polyamine curing agents and difunctional glycols(i.e., 3,5-dimethylthio-2,4-toluenediamine,3,5-dimethylthio-2,6-toluenediamine, N,N″-dialkyldiamino diphenylmethane, trimethyleneglycol-di-p-aminobenzoate,polytetramethyleneoxide-di-p-aminobenzoate, 1,4-butanediol,2,3-butanediol, 2,3-dimethyl-2,3-butanediol, ethylene glycol, andmixtures of the same). The polyurethane prepolymer in the '673 patent isdisclosed as made from a polyol (e.g., polyether, polyester, orpolylactone) and a diisocyanate such as MDI or TODI. The polyetherpolyols disclosed in the '673 patent are polytetramethylene etherglycol, poly(oxypropylene) glycol, and polybutadiene glycol. Thepolyester polyols disclosed in the '673 patent are polyethylene adipateglycol, polyethylene propylene adipate glycol, and polybutylene adipateglycol. The polylactone polyols disclosed in the '673 patent arediethylene glycol initiated caprolactone, 1,4-butanediol initiatedcaprolactone, trimethylol propane initiated caprolactone, and neopentylglycol initiated caprolactone.

[0020] Cavallaro, et al., U.S. Pat. No. 5,688,191 discloses a golf ballhaving core, mantle layer and cover, wherein the mantle layer is eithera vulcanized thermoplastic elastomer, functionalized styrene-butadieneelastomer, thermoplastic polyurethane, metallocene polymer or blends ofthe same and thermoset materials.

[0021] Wu, et al., U.S. Pat. No. 5,692,974 discloses golf balls havingcovers and cores that incorporate urethane ionomers (i.e. using analkylating agent to introduce ionic interactions in the polyurethane andthereby produce cationic type ionomers).

[0022] Sullivan, et al., U.S. Pat. No. 5,803,831 (the '831 patent)discloses a golf ball having a multi-layer cover wherein the inner coverlayer has a hardness of at least 65 Shore D and the outer cover layerhas a hardness of 55 Shore D or less, and more preferably 48 Shore D orless. The '831 patent explains that this dual layer constructionprovides a golf ball having soft feel and high spin on short shots, andgood distance and average spin on long shots. The '831 patent providesthat the inner cover layer can be made from high or low acid ionomerssuch as SURLYN Â®, ESCOR Â®or IOTEKÂ®, or blends of the same,nonionomeric thermoplastic material such as metallocene catalyzedpolyolefins or polyamides, polyamide/ionomer blends, polyphenyleneether/ionomer blends, etc., (having a Shore D hardness of at least 60and a flex modulus of more than 30000 psi), thermoplastic orthermosetting polyurethanes, polyester elastomers (e.g. HYTREL Â®), orpolyether block amides (e.g. PEBAX Â®), or blends of these materials.The “831 patent also provides that the outer cover layer can be madefrom soft low modulus (i.e. 1000-10000 psi) material such as low-acidionomers, ionomeric blends, non-ionomeric thermoplastic or thermosettingmaterials such as polyolefins, polyurethane (e.g. thermoplasticpolyurethanes like TEXINÂ®, PELETHANEÂ®, and thermoset polyurethaneslike those disclosed in Wu, U.S. Pat. No. 5,334,673), polyesterelastomer (e.g. HYTRELÂ®), or polyether block amide (e.g. PEBAXÂ®), or ablend of these materials.

[0023] Hebert, et al., U.S. Pat. No. 5,885,172 (the '172 patent)discloses a multilayer golf ball giving a progressive performance (i.e.different performance characteristics when struck with different clubsat different head speeds and loft angles) and having an outer coverlayer formed of a thermoset material with a thickness of less than 0.05inches and an inner cover layer formed of a high flexural modulusmaterial. The '172 patent provides that the outer cover is made frompolyurethane ionomers as described in Wu, et al., U.S. Pat. No.5,692,974, or thermoset polyurethanes such as TDI ormethylenebis-(4-cyclohexyl isocyanate) (HMDI), or a polyol cured with apolyamine (e.g. methylenedianiline (MDA)), or with a trifunctionalglycol (e.g., N,N,N″,N″-tetrakis(2-hydroxpropyl) ethylenediamine). The'172 also provides that the inner cover has a Shore D hardness of 65-80,a flexural modulus of at least about 65,000 psi, and a thickness ofabout 0.020-0.045 inches. Exemplary materials for the inner cover areionomers, polyurethanes, polyetheresters (e.g. HYTRELÂ®),polyetheramides (e.g., PEBAXÂ®)), polyesters, dynamically vulcanizedelastomers, functionalized styrene-butadiene elastomer, metallocenepolymer, blends of these materials, nylon oracrylonitrile-butadiene-styrene copolymer.

[0024] Wu, U.S. Pat. No. 5,484,870 (the '870 patent) discloses golfballs having covers composed of a polyurea composition. The polyureacomposition disclosed in the '870 patent is a reaction product of anorganic isocyanate having at least two functional groups and an organicamine having at least two functional groups. One of the organicisocyanates disclosed by the '870 patent is PPDI.

[0025] Although the prior art has disclosed golf ball covers composed ofmany different materials, none of these golf balls have provencompletely satisfactory. Dissatisfaction, for example, remains withprocessing and manufacturing the balls, and with the balls” durabilityand performance.

[0026] Specifically, with respect to processing, prior materials are notuser friendly because certain starting materials may be unhealthful,such as diamines and isocyanides. In addition, prior balls using suchmaterials are generally wound balls. Wound balls have tolerances thatare more difficult to control due to core sizes and/or windings sizes,and therefore, require thicker cover layers to account for themanufacturing tolerances. With respect to durability problems, priorpolyurethane covered balls, because they are wound balls, tend to losecompression and initial velocity due to the windings relaxing over timeand use. With respect to performance problems, prior balls, as a generalrule, tend to have smaller cores that result in shorter flightdistances. Although many golf balls having a polyurethane cover havebeen provided by the prior art, these golf balls have failed to capturethe sound and feel of balata while providing a golf ball with thedurability of an ionomer.

SUMMARY OF INVENTION

[0027] One aspect of the present invention is a golf ball having a solidcore, an intermediate layer and a cover. The core has a diameter of 1.35inches to 1.64 inches. The core is composed of a polybutadiene material,zinc oxide, zinc stearate, zinc diacryalate, a peroxide, and tungsten inan amount of 2 to 10 parts per hundred parts of polybutadiene. The corehas a PGA compression of 55 to 80 points.

[0028] Having briefly described the present invention, the above andfurther objects, features and advantages thereof will be recognized bythose skilled in the pertinent art from the following detaileddescription of the invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

[0029]FIG. 1 illustrates a perspective view of a golf ball of thepresent invention including a cut-away portion showing a core, aboundary layer, and a cover.

[0030]FIG. 2 illustrates a perspective view of a golf ball of thepresent invention including a cut-away portion core and a cover.

[0031]FIG. 3 illustrates a golf club hitting a golf ball.

[0032]FIG. 4 illustrates a cover shear testing apparatus.

[0033]FIG. 4A illustrates an isolated view of the golf ball holder forthe cover shear testing apparatus.

[0034]FIG. 4B illustrates an isolated view of the strike plate of thecover shear testing apparatus.

DETAILED DESCRIPTION

[0035] As illustrated in FIG. 1, the golf ball of the present inventionis generally indicated as 10. The golf ball 10 includes a core 12, aboundary layer 14 and a cover 16. Alternatively, as shown in FIG. 2, thegolf ball 10 may only include a core 12 and a cover 16.

[0036] The cover 16 is a polyurethane cover having a predeterminedhardness and a predetermined durability as measured on a cover strikeplate drop test as further described below. The polyurethane cover 16 iscomposed of a polyurethane material formed from a blend of diisocyanateprepolymers. The blend of diisocyanate prepolymers includes at least oneTDI-based polyurethane prepolymer and at least one otherdiisocyanate-based polyurethane prepolymer. In a preferred embodiment,the blend of diisocyanate prepolymers includes at least one PPDI-basedpolyurethane prepolymer and at least one TDI-based polyurethaneprepolymer. Alternative embodiments have a blend which includes at leasttwo different PPDI-based polyurethane prepolymer and at least oneTDI-based polyurethane prepolymer. Yet further embodiments may includeat least one TDI-based polyurethane prepolymer and at least oneMDI-based polyurethane prepolymer. Those skilled in the pertinent artwill recognize that multiple variations of diisocyanate prepolymers maybe utilized without departing from the scope and spirit of the presentinvention.

[0037] The polyurethane cover 16 encompasses a boundary layer 14, asshown in FIG. 1, or alternatively the cover 16 may encompass the core 12as shown in FIG. 2. The boundary layer 14 is composed of a thermoplasticmaterial that has a predetermined hardness. The boundary layer 14 willencompass the core 12. Each component of the golf ball 10 of the presentinvention will be described below in greater detail.

[0038] The most important feature of the present invention is thedurability of the cover. As shown in FIG. 3, the golf ball 10 issubjected to tremendous forces when impacted with a golf club 20 duringa golf shot. The golf ball 10 of the present is capable of enduring,more than polyurethane covered golf balls of the prior art, slices orother incorrect hits by golfers. The unique polyurethane formulation forthe cover 16 of the present invention provides this enhanced durability.Durability as defined herein is objectively measured through comparativetesting of available golf balls versus the golf ball 10 of the presentinvention. The testing methods and results will be described below.

[0039] The polyurethane utilized in the present invention is composed ofblend of a TDI-based prepolymer, a second diisocyanate-basedpolyurethane prepolymer and a curing agent. The TDI-based prepolymer ispreferably formed from TDI and a polyether polyol. The seconddiisocyanate-based polyurethane prepolymer is preferably a PPDI-basedprepolymer formed from PPDI and a polyester polyol, preferably apolycaprolactone. The prepolymer blend is cured with a curing agent. Thecuring agent, or curative, may be a diol (e.g., 1,4 butane diol,trimethylpropanol), a mixture of diols (e.g., 1,4 butane diol andethylene glycol, or other suitable glycols), a hydroquinone, a mixtureof hydroquinones, a triol, a mixture of triols, a diamine, a mixture ofdiamines, an oligomeric diamine, a triamine, or a blend of some or allof these materials. Preferably, the curing agent is a blend of a diamineand a mixture of diols.

[0040] In an alternative embodiment, the blend of prepolymers includesthree diisocyanate-based polyurethane prepolymers. In this embodiment,the TDI-based prepolymer is preferably formed from TDI and a polyetherpolyol. The second diisocyanate-based polyurethane prepolymer ispreferably a PPDI-based prepolymer formed from PPDI and a polyesterpolyol, preferably a polycaprolactone. The third diisocyanate-basedpolyurethane prepolymer is a PPDI-based prepolymer formed from PPDI anda polyether polyol. Preferably, the curing agent is a blend of a diamineand a mixture of diols. As mentioned above, alternative embodiments mayhave variations of the dual blend or the tri-blend, and may use aTDI-based polyurethane prepolymer with other non-PPDI-based polyurethaneprepolymers.

[0041] As previously set forth in this Assignee's U.S. Pat. No.6,117,024, entitled Golf Ball With Polyurethane Cover, filed on Apr. 20,1999, which is hereby incorporated by reference in its entirety, aPPDI-based polyurethane prepolymer provides a polyurethane with a higherrebound at a lower hardness, greater durability and improved sound andfeel. However, although the use of only a PPDI-based polyurethaneprepolymer provides greater durability for a polyurethane cover, thepolyurethane cover 16 of the present invention formed from a blend ofprepolymers provides even greater durability.

[0042] The blending of a TDI-based prepolymer with otherdiisocyanate-based polyurethane prepolymers lowers the viscosity of themixture, lowers the temperature of the exothermic reaction that occurswhen the prepolymers are reacted with the curing agent, and increasesthe durability. The TDI-based prepolymer may range from 10 to 40 percentof the polyurethane prepolymer blend.

[0043] Preferably, the TDI-based prepolymer is 30 percent of thepolyurethane prepolymer blend. A preferred TDI based prepolymer is a TDIterminated polyether prepolymer available from Uniroyal Chemical Companyof Middlebury, Connecticut, under the tradename ADIPRENEÂ®Â®LF950.

[0044] The dual blend and tri-blend formulations will preferably containa PPDI terminated polyester prepolymer and/or a PPDI terminatedpolyether prepolymer. A preferred PPDI terminated polyester prepolymeris available from Uniroyal Chemical under the tradename ADIPRENEÂ® LFPX2950. A preferred PPDI terminated polyether prepolymer is available fromUniroyal Chemical under the tradename ADIPRENEÂ® LFPX 950.

[0045] The polyurethane prepolymer blend may have 10 to 40 parts of aTDI terminated polyether prepolymer blended with 60 to 90 parts of aPPDI terminated polyether prepolymer. Alternatively, the polyurethaneprepolymer blend may have 10 to 40 parts of a TDI terminated polyetherprepolymer blended with 60 to 90 parts of a PPDI terminated polyesterprepolymer. Further, the polyurethane prepolymer blend may have 10 to 40parts of a TDI terminated polyether prepolymer blended with 5 to 90parts of a PPDI terminated polyether prepolymer and 5 to 90 parts of aPPDI terminated polyester prepolymer. More specific blend formulationsare set forth in the Examples below.

[0046] The cover 16 of the golf ball 10 of the present invention is mostpreferably composed of a polyurethane formed from a polyurethaneprepolymer blend composed of a TDI-based polyurethane prepolymer and aPPDI-based polyurethane prepolymer, and cured with a mixture of curingagents such as a diamine and a blend of 1,4 butane diol and glycols. Asuitable blend of diol and glycols is available from Uniroyal Chemicalunder the tradename VIBRACURE Â® A250. A suitable diamine is tolueneethylene diamine available from Albemarle Corporation of Baton Rouge,La. under the tradename ETHACUREÂ® 100. Other agents which may beutilized during the curing process includedimethylthio-2,4-toluenediamine (such as EHTACUREÂ®300 available fromAlbemarle Corporation); trimethyl glycol di-p-aminobenzoate (such asVERSALINKÂ® 740M available from Air Products and Chemicals, Inc.,Allentown, Pa.); cyclohexane dimethanol; hydroquinone-bis-hydroxyethylether; phenyldiethanol amine mixture (such as VIBRACURE Â® A931available from Uniroyal Chemical); methylene dianiline sodium chloridecomplex (such as CAYTORÂ® 31 available from Uniroyal Chemical); and/orprionene amine. This list of preferred agents (including chainextenders, cross-linkers and curing agents) is not meant to beexhaustive, as any suitable (preferably polyfunctional) chain extender,cross-linker, or curing agent may be used.

[0047] The curing agent mixture for the cover 16 of the presentinvention may have numerous variations. In a preferred embodiment, thecuring agent is composed of 30 to 70 parts of a diol blend such asVIBRACUREÂ®250 to 70 to 30 parts of a diamine such as ETHACUREÂ®300.Alternatively, the diamine component may be a blend of differentdiamines such as a blend of EHTACUREÂ®100 with ETHACUREÂ®300.

[0048] The ratio of the polyurethane prepolymer blend to curing agent isdetermined by the nitrogen-carbon-oxygen group (NCO) content of thepolyurethane prepolymer blend. For example, the NCO content of theTDI-terminated polyether or TDI-terminated polyester is preferably inthe range of 4.0% to 9.0%, while the NCO content of the PPDI-terminatedpolyether is preferably in the range of 5.0% to 8.0%. The NCO content ofthe PPDI-terminated polyester is preferably in the range of 2.0% to6.0%. The NCO content of the polyurethane prepolymer blend ranges from2% to 8% of the polyurethane prepolymer blend. The amount of curingagent should correspond to 90% to 110% of the mol equivalence of the NCOcontent of the polyurethane prepolymer blend. The weight ratio of thepolyurethane prepolymer blend to the curing agent is preferably in therange of about 10:1 to about 30:1.

[0049] Prior to curing, the polyurethane prepolymer blend and curingagent are preferably stored separately. The polyurethane is formed byfirst heating and mixing the polyurethane prepolymer blend with thecuring agent in a mold, and then curing the mixture by applying heat andpressure for a predetermined time period. Additionally, a catalyst (e.g.dibutyl tin dilaurate, a tertiary amine, etc.) may be added to themixture to expedite the casting process. Specific suitable catalystsinclude TEDA dissolved in di propylene glycol (such as TEDA L33available from Witco Corp. Greenwich, Conn., and DABCO 33 LV availablefrom Air Products and Chemicals Inc.,) which may be added in amounts of2-5%, and more preferably TEDA dissolved in 1,4-butane diol which may beadded in amounts of 2-5%. Another suitable catalyst includes a blend of0.5% 33LV or TEDA L33 (above) with 0.1% dibutyl tin dilaurate (availablefrom Witco Corp. or Air Products and Chemicals, Inc.) which is added toa curative such as VIBRACURE Â® A250. Furthermore, additives such ascolorants may also be added to the mixture.

[0050] The polyurethane prepolymer blend material is preferably degassedand warmed in a first holding container prior to processing of the cover16. The processing temperature for the polyurethane prepolymer blend ispreferably in the range of about 100-220Â° F., and most preferably inthe range of about 120-200Â° F. The polyurethane prepolymer blend ispreferably flowable from the first holding container to a mixing chamberin a range of about 200-1100 grams of material per minute, or as neededfor processing. In addition, the polyurethane prepolymer blend materialmay be agitated in the first holding container, in the range of 0-250rpm, to maintain a more even distribution of material and to eliminatecrystallization.

[0051] In the preferred embodiment, the curing agent is a blend of adiamine such as ETHACUREÂ®300 and a 1,4 butane diol and glycol such asVIBRACURE Â A250. As previously mentioned, other curatives may also beutilized in forming the cover 16 of the golf ball 10 of the presentinvention. The curing agent is preferably degassed and warmed in asecond holding container prior to processing of the cover 16. Theprocessing temperature for the curative is preferably in the range ofabout 50-230Â° F., and most preferably in the range of about 80-200Â° F.The curing agent is preferably flowable from the second holdingcontainer to the mixing chamber in the range of about 15-75 grams ofmaterial per minute, or as needed. If a catalyst is used for processingthe cover 16, then the catalyst is added to the curing agent in thesecond holding container to form a curative mixture. Suitable catalystare described above. The curing agent and catalyst are agitated, in therange of about 0 to 250 rpm, to maintain an even distribution ofcatalyst in the curative mixture in the second holding container. It ispreferred that the catalyst is added in an amount in the range of about0.25-5% by weight of the combined polyurethane prepolymer blend andcuring agent. Additives may be added to the curative mixture as desired.It was discovered that hydrolytic instability of the polyurethanepolymer may be avoided by the addition of a stabilizer such asSTABOXYLÂ® (available from Rheinchemie, Trenton, N.J.), in amounts ofabout 0.25-5% of the polyurethane.

[0052] The polyurethane prepolymer blend and curative mixture arepreferably added to the common mixing chamber at a temperature in therange of about 160-220Â° F. A colorant material, such as, for example,titanium dioxide, barium sulfate, and/or zinc oxide in a glycol orcastor oil carrier, and/or other additive material(s) as are well knownin the art, may be added to the common mixing chamber. The amount ofcolorant material added is preferably in the range of about 0-10% byweight of the combined polyurethane prepolymer blend and curativematerials, and more preferably in the range of about 2-8%. Otheradditives, such as, for example, polymer fillers, metallic fillers,and/or organic and inorganic fillers (e.g. polymers, balata, ionomers,etc.) may be added as well to increase the specific gravity of thepolyurethane cover 16 of the present invention. It was discovered thatthe addition of barytes (barium sulfate) or a blend of barytes andtitanium dioxide (preferably added in a carrier glycol and/or castoroil) to the mixture, in the amounts of about 0.01-30%, may addsufficient weight to the polyurethane cover 16. The added weight to thecover 16 allows for a lower specific gravity for the core 12 therebyallowing for an increased resiliency of the core 12. The entire mixtureis preferably agitated in the mixing chamber in the range of about 1 to250 rpm prior to molding. A more detailed explanation of the process isset forth in U.S. Pat. No. 6,200,512, entitled Golf Balls And Methods OfManufacturing The Same, filed on Apr. 20, 1999, which is herebyincorporated by reference in its entirety.

[0053] The core 12 of the golf ball 10 is the engine for the golf ball10 such that the inherent properties of the core 12 will stronglydetermine the initial velocity and distance of the golf ball 10. Ahigher initial velocity will usually result in a greater overalldistance for a golf ball. In this regard, the Rules of Golf, approved bythe United States Golf Association (USGA) and The Royal and Ancient GolfClub of Saint Andrews, limits the initial velocity of a golf ball to 250feet (76.2m) per second (a two percent maximum tolerance allows for aninitial velocity of 255 per second) and the overall distance to 280yards (256 m) plus a six percent tolerance for a total distance of 296.8yards (the six percent tolerance may be lowered to four percent). Acomplete description of the Rules of Golf are available on the USGA webpage at www.usga.org. Thus, the initial velocity and overall distance ofa golf ball must not exceed these limits in order to conform to theRules of Golf. Therefore, the core 12 for a USGA approved golf ball isconstructed to enable the golf ball 10 to meet, yet not exceed, theselimits.

[0054] The coefficient of restitution (“COR”) is a measure of theresilience of a golf ball. The COR is a measure of the ratio of therelative velocity of the golf ball after direct impact with a hardsurface to the relative velocity before impact with the hard surface.The COR may vary from 0 to 1, with 1 equivalent to a completely elasticcollision and 0 equivalent to a completely inelastic collision. A golfball having a COR value closer to 1 will generally correspond to a golfball having a higher initial velocity and a greater overall distance.The effect of a higher COR value is illustrated in FIG. 3 in which agolf club 20 strikes the golf ball 10. The force of the club 20 during aswing is transferred to the golf ball 10. If the golf ball has a highCOR (more elastic), then the initial velocity of the golf ball will begreater than if the golf ball had a low COR. In general, a highercompression core will result in a higher COR value.

[0055] The core 12 of the golf ball 10 is generally composed of a blendof a base rubber, a cross-linking agent, a free radical initiator, andone or more fillers or processing aids. A preferred base rubber is apolybutadiene having a cis-1,4 content above 90%, and more preferably98% or above.

[0056] The use of cross-linking agents in a golf ball core is wellknown, and metal acrylate salts are examples of such cross-linkingagents. For example, metal salt diacrylates, dimethacrylates, or mono(meth)acrylates are preferred for use in the golf ball cores of thepresent invention, and zinc diacrylate is a particularly preferredcross-linking agent. A commercially available suitable zinc diacrylateis SR-416 available from Sartomer Co., Inc., Exton, Pa. Other metal saltdi- or mono-(meth)acrylates suitable for use in the present inventioninclude those in which the metal is calcium or magnesium. In themanufacturing process it may be beneficial to pre-mix some cross-linkingagent(s), such as, e.g., zinc diacrylate, with the polybutadiene in amaster batch prior to blending with other core components.

[0057] Free radical initiators are used to promote cross-linking of thebase rubber and the cross-linking agent. Suitable free radicalinitiators for use in the golf ball core 12 of the present inventioninclude peroxides such as dicumyl peroxide, bis-(t-butyl peroxy)diisopropyl benzene, t-butyl perbenzoate, di-t-butyl peroxide,2,5-dimethyl-2,5-di-5-butylperoxy-hexane, 1,1-di (t-butylperoxy)3,3,5-trimethyl cyclohexane, and the like, all of which are readilycommercially available.

[0058] Zinc oxide is also preferably included in the core formulation.Zinc oxide may primarily be used as a weight adjusting filler, and isalso believed to participate in the cross-linking of the othercomponents of the core (e.g. as a coagent). Additional processing aidssuch as dispersants and activators may optionally be included. Inparticular, zinc stearate may be added as a processing aid (e.g. as anactivator). Any of a number of specific gravity adjusting fillers may beincluded to obtain a preferred total weight of the core 12. Examples ofsuch fillers include tungsten and barium sulfate. All such processingaids and fillers are readily commercially available. The presentinventors have found a particularly useful tungsten filler is WP102Tungsten (having a 3 micron particle size) available from AtlanticEquipment Engineers (a division of Micron Metals, Inc.), Bergenfield,N.J.

[0059] Table 1 below provides the ranges of materials included in thepreferred core formulations of the present invention. TABLE 1 CoreFormulations Component Preferred Range Most Preferred RangePolybutadiene 100 parts 100 parts Zinc diacrylate 20-35 phr 25-30 phrZinc oxide  0-50 phr  5-15 phr Zine stearate  0-15 phr  1-10 phrPeroxide 0.2-2.5 phr 0.5-1.5 phr Filler As desired As desired (e.g.tungsten) (e.g. 2-10 phr) (e.g. 2-10 phr)

[0060] In the present invention, the core components are mixed andcompression molded in a conventional manner known to those skilled inthe art. In a preferred form, the finished core 12 has a diameter ofabout 1.35 to about 1.64 inches for a golf ball 10 having an outerdiameter of 1.68 inches. The core weight is preferably maintained in therange of about 32 to about 40 g. The core PGA compression is preferablymaintained in the range of about 50 to 90, and most preferably about 55to 80.

[0061] As used herein, the term PGA compression is defined as follows:PGA compression value=180 Riehle compression value. The Riehlecompression value is the amount of deformation of a golf ball in inchesunder a static load of 200 pounds, multiplied by 1000. Accordingly, fora deformation of 0.095 inches under a load of 200 pounds, the Riehlecompression value is 95 and the PGA compression value is 85.

[0062] As is described above, the present invention preferably includesat least one boundary layer 14 that preferably is composed of athermoplastic (e.g. thermoplastic or thermoplastic elastomer) or a blendof thermoplastics (e.g. metal containing, non-metal containing or both).However, the golf ball 10 may have several boundary layers 14 disposedbetween the core 12 and the cover 16. Most preferably the boundary layer14 is composed of at least one thermoplastic that contains organic chainmolecules and metal ions. The metal ion may be, for example, sodium,zinc, magnesium, lithium, potassium, cesium, or any polar metal ion thatserves as a reversible cross-linking site and results in high levels ofresilience and impact resistance. Suitable commercially availablethermoplastics are ionomers based on ethylene copolymers and containingcarboxylic acid groups with metal ions such as described above. The acidlevels in such suitable ionomers may be neutralized to controlresiliency, impact resistance and other like properties. In addition,other fillers with ionomer carriers may be used to modify (e.g.preferably increase) the specific gravity of the thermoplastic blend tocontrol the moment of inertia and other like properties. Exemplarycommercially available thermoplastic materials suitable for use in aboundary layer 14 of a golf ball 10 of the present invention include,for example, the following materials and/or blends of the followingmaterials: HYTRELÂ®and/or HYLENEÂ®Â® products from DuPont, Wilmington,Del., PEBAXÂ®products from Elf Atochem, Philadelphia, Pa., SURLYNÂ®products from DuPont, and/or ESCORÂ® or IOTEKÂ® products from ExxonChemical, Houston, Tex.

[0063] The Shore D hardness of the boundary layer 14 should be about 65or less. It is preferred that the boundary layer 14 have a hardness ofbetween about 50-65 Shore D. In a preferred embodiment, the boundarylayer 14 has a Shore D hardness in the range of about 57-65. One reasonfor preferring a boundary layer 14 with a Shore D hardness of 65 orlower is to improve the feel of the resultant golf ball. It is alsopreferred that the boundary layer 14 is composed of a blend of SURLYNÂ®ionomer resins. SURLYNÂ®8150, 9150, and 6320 are, respectively, anionomer resin composed of a sodium neutralized ethylene/methacrylicacid, an ionomer resin composed of a zinc neutralizedethylene/methacrylic acid, and an ionomer resin composed of a terpolymerof ethylene, methacrylic acid and n-butyl acrylate partially neutralizedwith magnesium, all of which are available from DuPont, PolymerProducts, Wilmington, Del.

[0064] The boundary layer 14 may include a predetermined amount of abaryte mixture. The baryte mixture is included as 8 or 9 parts perhundred parts of the ionomer resins. One preferred baryte mixture iscomposed of 80% barytes and 20% of an ionomer, and is available fromAmerichem, Inc., Cuyahoga Falls, Ohio, under the trade designation38534X1. The Shore D hardness provided in Table Three below wasdetermined according to ASTM D2240.

[0065] Twelve golf balls of the present invention were compared to aMaxfli REVOLUTION, a Titlelist PROFESSIONAL, a Titlelist DT-2, and aBridgestone PRECEPT. All of the golf balls were subjected to adurability test to determine the durability of the golf balls in anobjective manner. The durability tests were conducted on a cover shearapparatus as illustrated in FIGS. 4, 4A and 4B. The apparatus 30includes a ten pound metal block 32 with a strike plate 34 on itsbottom, mounted on a frame 36. A golf ball 10 is placed within a holder38 and held by a set of pins 40. The strike plate 34 is angled at 54degrees from vertical. The strike plate 34 is dropped from six inchesabove the golf ball 10.

[0066] The golf balls are measured on a cover shear criteria. The scalefor each is from 1 to 5, with 1 being poor, 2 being below average, 3being average, 4 being above average and 5 being excellent. The covershear criteria is as follows: 1-portion of the cover has been completelysheared off and dimples have been greatly reduced or removed; 2-thecover material has been sheared to the extent that the flaps of thecover are visible, and severe bunching or peeling back of the covermaterial is evident; 3-there is moderate cutting of the cover materialto the extent that internal portions of the cover are exposed, but thecover is intact; 4-indentations in the cover are evident, but there isno bunching of the cover material ; 5-groove marks are difficult to seeand slight score marks may or may not be visible, and there is nodeformation of the cover material.

[0067] Table Two below sets forth physical data for suitable boundarylayers 14 t were manufactured and incorporated into specific embodimentsof twelve example golf balls of the present invention. As is shown inTable 3 below, each of the boundary layers 14 were composed of anionomer blend and specific percentages are provided. The thickness ofeach of the boundary layers 14 varies from 0.0525 and 0.058 inches. Theshore D hardness var between 58 and 62. TABLE TWO Ball SURLYN ®Thickness Shore D Ex. No. % 8150 % 9150 % 6320 (inches) Hardness 1 40 4020 0.058 58 2 45 45 10 0.0525 62 3 45 45 10 0.0525 62 4 40 40 20 0.05860 5 40 40 20 0.058 60 6 40 40 20 0.058 60 7 45 45 20 0.0525 62 8 45 4520 0.0525 62 9 45 45 10 0.0525 62 10 45 45 10 0.0525 62 11 45 45 100.0525 62 12 45 45 10 0.0525 62

[0068] TABLE THREE Ball Ball Average Core Core Weight CompressionDiameter Diameter Compression

(grams) (points) (inches) (inches) (points) 45.65 92 1.684 1.489 6045.86 98 1.684 1.515 70 45.92 101 1.684 1.515 75 45.82 94 1.684 1.489 6045.83 99 1.684 1.489 65 45.90 99 1.684 1.489 65 45.86 96 1.684 1.515 7045.84 100 1.684 1.515 75 45.84 101 1.684 1.515 75 45.89 98 1.684 1.51565 45.83 95 1.682 1.515 65 45.84 97 1.681 1.515 69

[0069] Table Four sets forth the properties of each of the cover layers16 for each the twelve golf balls 10. The number of parts of eachpolyurethane prepolymer for each of the cover layers 16 is provided incolumns 2 through 6. Column includes the number of parts of theTDI-terminated polyether prepolymer, ADIPRENEÂ®LF950. Column 3 includesthe number of parts of the PPDI terminated polyether prepolymer,ADIPRENEÂ® LFPX950. Column 4 includes the number of parts of the PPDIterminated polyester (polycaprolactone) prepolymer, ADIPRENEÂ®LFPX2950.Column 5 includes the number of parts of the PPDI terminated polyetherprepolymer, ADIPRENEÂ® LFPX590. The difference between LFPX590 andLFPX950 is the NCO content and the molecular weight of the polyol(ether) backbone, with LFPX950 having a NCO content in the range ofapproximately 5.45% to approximately 5.75%, and LFPX590 having a NCOcontent in the range of approximately 5.6% to approximately 6.2%. Column6 includes the number of parts of the PPDI terminated polyester(polycaprolactone) prepolymer, ADIPRENEÂ® LFPX2952. The differencebetween LFPX2950 and LFPX2952 is the NCO content, with LFPX2950 having aNCO content in the range of approximaely 3.55% to approximately 3.85%,and LFPX2952 having a NCO content in the range of approximately 4.45% toapproximately 5.05%. Each of the polyurethane prepolymer blends forexamples 1-9 and 11-12 were cured with a blend of curing agents. Theblend of curing agents was composed of 50 parts ETHACURE 300 (a diaminecuring agent) and 50 parts VIBRACURE A250 ( a blend of a 1,4 butane dioland glycol). Example 10 of the golf ball of the present invention wascured with a blend of 70 parts ETHACURE 3 and 30 parts VIBRACURE A250.The thickness of the cover layer 16 for each of the twelve golf balls 10of present invention is either 0.0300 inches or 0.0375 inches. The shoreD hardness of the cover layer 16 for each of the twelve golf balls 10 ofpresent invention is either 47 degrees or 53 degrees TABLE FOUR BallThick- Ex. Polyurethane prepolymer ness Shore D No. TDI PPDI-1 PPDI-2PPDI-3 PPDI-4 (inches) Hardness 1 30 70 0.0375 47 2 30 20 50 0.0300 53 330 70 0.0300 47 4 30 70 0.0375 47 5 30 50 20 0.0375 47 6 30 70 0.0375 477 30 50 20 0.0300 47 8 30 20 50 0.0300 53 9 30 70 0.0300 47 10 20 800.0300 47 11 30 70 0.0300 47 12 30 70 0.0300 47

[0070] TABLE FIVE 110 mph Drive 90 mph Drive 79 mph 5-Iron Shear CarryTotal Carry Total Carry

(1-5) (yds) (yds) (yds) (yds) (yds)

olution 5 251.5 269.6 194.5 218.6 158.1

cept EV 4 253.1 270.6 196.2 220.4 162.7

fessional 4 248.2 266.1 190.3 216.0 158.4

2-piece 1 256.1 274.7 197.1 222.8 164.8 4.25 253.9 271.1 195.7 220.6161.2 4.0 255.5 274.1 196.7 222.4 163.2 4.0 257.3 272.2 199.2 221.8162.0 4.0 253.9 269.7 197.0 220.4 160.4 4.0 254.3 274.1 198.2 220.4159.1 4.25 254.4 269.4 197.4 220.6 160.1 4.25 255.9 271.4 198.3 221.9161.6 3.75 257.2 273.2 198.2 222.7 163.6 3.75 256.8 273.6 197.2 222.7163.8 3.75 256.7 275.5 197.5 222.6 161.3 4.5 255.5 273.3 196.8 222.5160.9 4.5 257.3 274.2 196.8 221.5 161.1

[0071] Table Five illustrates the comparison testing between the twelvesample golf balls 10 of the present invention, and the four well-knownand well-played golf balls. All of the golf balls in Table Six weresubjected to the afore-mentioned shear test and rated. The golf ballswere also subject to a standard robot swing test at 110 miles per hour(mph) using a BIG BERTHAÂ®HAWKEYE Â® driver, at 90 mph using a BIGBERTHAÂ®HAWKEYE Â®driver, and at 79 mph using a BIG BERTHAÂ®X-12Â®(fiveiron. Although the REVOLUTIONÂ®had the best shear rating, its carry andtotal distance was only better than the Titlelist PROFESSIONALÂ®.Example 12 of the golf balls 10 of the present invention had adurability rating of 4.5, and it had a carry six yards better than theREVOLUTION at 110 mph using a BIG BERTHAÂ®HAWKEYE Â®driver. The bestdistance at 110 mph using a BIG BERTHAÂ®HAWKEYE Â®driver was example 10of the golf balls 10 of the present invention which had a carry yardageof 256.7 yards and a total distance of 275.5 yards with a durability of3.75. The next closest golf ball in distance was the DT-2, however, itonly had a durability of 1. Table Six demonstrates that the golf ball 10of the present invention provides objectively the best overalldurability with the best overall distance.

[0072] The above examples demonstrate the efficacy of the golf ball 10of the present invention and are not intended to limit the scope orspirit of the present invention.

[0073] From the foregoing it is believed that those skilled in thepertinent art will recognize the meritorious advancement of thisinvention and will readily understand that while the present inventionhas been described in association with a preferred embodiment thereof,and other embodiments illustrated in the accompanying drawings, numerouschanges, modifications and substitutions of equivalents may be madetherein without departing from the spirit and scope of this inventionwhich is intended to be unlimited by the foregoing except as may appearin the following appended claims. Therefore, the embodiments of theinvention in which an exclusive property or privilege is claimed aredefined in the following appended claims.

We claim as our invention:
 1. A golf ball comprising: a core having adiameter of 1.35 inches to 1.64 inches, the core comprisingpolybutadiene material, zinc oxide in an amount of 5 to 15 parts perhundred parts of polybutadiene, zinc stearate in an amount of 1 to 10parts per hundred parts of polybutadiene, zinc diacryalate in an amountof 20 to 35 parts per hundred parts of polybutadiene, and a peroxide inan amount of 0.5 to 1.5 parts per hundred parts of polybutadiene, thecore having a PGA compression of 55 to 80 points; an intermediate layercovering the core, the intermediate layer having a Shore D hardnessranging from 50 to 65; a cover enclosing the intermediate layer, thecover composed of a thermoset polyurethane material.
 2. A golf ballcomprising: a core having a diameter of 1.35 inches to 1.64 inches, thecore comprising polybutadiene material, zinc oxide in an amount of 5 to15 parts per hundred parts of polybutadiene, zinc stearate in an amountof 1 to 10 parts per hundred parts of polybutadiene, zinc diacryalate inan amount of 20 to 35 parts per hundred parts of polybutadiene, and aperoxide in an amount of 0.5 to 1.5 parts per hundred parts ofpolybutadiene, the core having a PGA compression of 55 to 80 points; anintermediate layer covering the core, the intermediate layer composed ofa blend of ionomers and having a Shore D hardness ranging from 50 to 65;a cover enclosing the intermediate layer, the cover composed of athermoset polyurethane material; wherein the golf ball has a PGAcompression ranging from 92 to 101 points, and the golf ball has a massof 45.65 grams to 45.92 grams.
 3. A golf ball comprising: a core havinga diameter of 1.35 inches to 1.64 inches, the core comprisingpolybutadiene material, zinc oxide in an amount of 5 to 15 parts perhundred parts of polybutadiene, zinc stearate in an amount of 1 to 10parts per hundred parts of polybutadiene, zinc diacryalate in an amountof 20 to 35 parts per hundred parts of polybutadiene, and a peroxide inan amount of 0.5 to 1.5 parts per hundred parts of polybutadiene, thecore having a PGA compression of 55 to 80 points; an intermediate layercovering the core, the intermediate layer composed of a blend ofionomers and having a Shore D hardness ranging from 50 to 65; a coverenclosing the intermediate layer, the cover composed of a thermosetpolyurethane material formed from a blend of polyurethane prepolymersand at least one curing agent; wherein the golf ball has a PGAcompression ranging from 92 to 101 points, the golf ball has a mass of45.65 grams to 45.92 grams, and the golf ball has a diameter ofapproximately 1.68 inches.